Makers of footwear strive to offer as many as possible of the desirable functions the consumer has come to expect. In addition to meeting the ancient needs for protection from heat, cold, and trauma, the modern consumer expects to take long walks without suffering foot fatigue or irritation, to walk, run, and jump with minimal impact upon joints and vertebrae, to stand comfortably for prolonged periods, and to be free of fungal infections and offensive foot odor. The consumer also expects footwear to be lightweight, durable, affordable, beautiful, and stylish. A designer's challenge in cultivating and meeting these expectations in a competitive market is limitless. A well-designed sole or footpad is central to meeting this challenge.
Many designs for soles and footpads reflect an attempt to cushion the body from the impact of footfalls by softening and thickening the sole or footpad. While effective at absorbing shock, such a solution might not always support the foot in a way which avoids fatigue and irritation. The softer materials used in these designs, especially foams, are sometimes less durable or more likely to retain moisture, dirt, and odor. Under some circumstances, a thick sole of solid rubber or a similar material would be too heavy. Finally, a thick sole or footpad is inappropriate for some styles of footwear.
Some proposed structures for soles and footpads reflect an attempt to ventilate the interior of the shoe. Ranging from simple to exotic, these structures have taken several different, although overlapping, approaches. One approach has been to employ various interconnected pumping chambers, bladders, valves, jets, tubes, orifices, and the like. Patents exemplifying this approach include U.S. Pat. Nos. 3,180,039; 3,225,463; 4,215,492; 4,499,672; 4,654,982; 4,760,651; 4,776,109; 4,860,463; 5,010,661; 5,224,277; 5,282,324; 5,341,581; 5,606,806; 5,787,609; 5,809,665; 5,815,949; 5,813,141; and 5,826,349. The structures shown, for the most part, use the motion of walking to agitate or exchange air surrounding the foot. Some of the structures also are described as cushioning the foot. To varying degrees, these structures add to the thickness, complexity, or cost of the product. Also to varying degrees, these structures provide inaccessible spaces where water or dirt can accumulate. Finally, these structures may be prone to rupture or other failure.
A related approach to ventilation, and one which also sometimes described as cushioning the foot, employs compressible supporting structures situated in a space defined between upper and lower layers of a footpad or insole. Patents exemplifying this approach include U.S. Pat. Nos. 3,716,930; 4,223,455; 4,364,186; 4,590,689; 4,674,203; 4,910,882; 5,035,068; 5,619,809; 5,669,161; 5,675,914, and 5,845,418. To varying degrees, the structures shown experience some of the aforementioned drawbacks relating to thickness, complexity, cost, dirt, and failure.
A third approach to ventilation employs a sole or insole having ribs, beads, liquid cells, knobs, or nipples. Patents exemplifying this approach include U.S. Pat. Nos. 4,685,224; 4,831,749; 5,167,999; 5,607,749; and 5,694,705. The structures shown, for the most part, use the motion of walking to agitate or exchange the air that flows between the foot and the footpad, or between and around the ribs, nipples, or the like. Some of these structures are also described as supporting, cushioning, or massaging the foot. While some of these structures might provide less cushioning or less support than a wearer would like, they are, for the most part, simpler, lighter, and thinner than those taking the other two approaches. The versatility of these thinner, simpler structures suggests that it would be desirable to optimize the performance of products taking this general approach.
The need persists for improved soles and footpads which deliver superior combinations of the above-described desirable functions. What is especially needed is a relatively thin, simple, easily made, lightweight, durable, well ventilated sole or footpad which provides good support for walking, shock absorption, and comfortable static support.